21721269 has 12 divisors (see below), whose sum is σ = 30277856. Its totient is φ = 13850232.

The previous prime is 21721253. The next prime is 21721277. The reversal of 21721269 is 96212712.

It is not a de Polignac number, because 21721269 - 2⁴ = 21721253 is a prime.

It is a super-2 number, since 2×21721269² = 943627053940722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21721229) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5257 + ... + 8430.

Almost surely, 2^21721269 is an apocalyptic number.

It is an amenable number.

21721269 is a deficient number, since it is larger than the sum of its proper divisors (8556587).

21721269 is a wasteful number, since it uses less digits than its factorization.

21721269 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13736 (or 13713 counting only the distinct ones).

The product of its digits is 3024, while the sum is 30.

The square root of 21721269 is about 4660.6082221101. The cubic root of 21721269 is about 279.0155436414.

It can be divided in two parts, 2 and 1721269, that added together give a palindrome (1721271).

The spelling of 21721269 in words is "twenty-one million, seven hundred twenty-one thousand, two hundred sixty-nine".